This application relates to a unique arrangement of bleed taps for compressed air for use on an aircraft associated with a gas turbine engine.
Gas turbine engines are known and utilized on aircraft. In a known gas turbine engine, a fan delivers air into a compressor section where the air is compressed. Typically, there are at least two compressor rotors with a lower pressure compressor and a higher pressure compressor. The compressed air is delivered into a combustion section where it is mixed with fuel and ignited. Products of this combustion pass downstream over at least two turbine rotors driving them to rotate. The turbine rotors, in turn, cause the fan rotor and compressor rotors to rotate.
While the gas turbine engine is utilized as a source of propulsion, it also supplies power and air to an associated aircraft. Thus, it is known to tap compressed air, typically, from an intermediate or downstream location associated with the higher pressure compressor rotor. The tapped air is utilized for various purposes and, in particular, delivered to an air pack where air is processed for use as environmental air, such as in a cabin of an associated aircraft. The air also provides other functions, such as pressurizing the fuselage of the aircraft.
The air tapped from these high pressure compressor locations has variable temperature and pressure, dependent on the point of the operation of the associated aircraft. As an example, at high energy times, such as take-off, the pressures are very high.
At times, the pressure is far too high as are the temperatures for the intended uses. Thus, it is known to pass the air from the high pressure compressor tap through a heat exchanger.
The fans in typical aircraft gas turbine engines deliver a portion of the air into a bypass duct where it is utilized as propulsion air and another portion into the low pressure compressor.
The air in the bypass duct is utilized to cool the tapped air.
Further conditioning is performed at the air conditioning pack and before the air is delivered into the cabin.
Thus, in particular at high power operation, the tapped high pressure compressor air must be cooled and lowered in pressure before being utilized on these aircraft functions or further conditioned at the air conditioning pack.
This results in loss of efficiency as the air has been compressed and then has its pressure lowered. In addition, a portion of fan air, which is otherwise used for propulsion, is undesirably heated in the heat exchanger.
These losses of efficiency not only simply cost fuel, they also raise challenges. As an example, due to the inefficient operation, the temperatures from the higher pressure turbine rotor reaching the last stage of turbine rotor are undesirably high. Thus, a mid-turbine duct, which serves to condition the flow of the product of combustion between the turbine rotors must be highly engineered and may need to include expensive materials.